1. Field of the Invention
The present invention relates to a ramp-position detecting device that detects and stores a ramp position to which a head of a storage medium is retracted, a ramp-position detecting method, and a storage device.
2. Description of the Related Art
To achieve high impact resistance, magnetic disks, such as hard disk drive (HDD), use a load/unload system. In the load/unload system, when a magnetic disk is not rotating, a head is retracted to a sloped portion called a ramp in the outermost periphery of the magnetic disk, and when the magnetic disk is rotating at a slow speed to be activated or stopped, the head is slid onto the ramp. Thus, when data reading or writing is not taking place, the head is prevented from coming in contact with a surface of the magnetic disk, which achieves the magnetic disk with high impact resistance.
In the load/unload system, in actual use (unloading) at the user-end, the ramp position needs to be stored beforehand so that the head can move to the ramp position. Various technologies have been proposed for detecting the ramp position.
For example, Japanese Patent Application Laid-open No. 2004-234806 discloses a technology whereby a control range of servo information is kept narrow at all times, and a position of a head where the speed of the head changes (i.e., the speed slows down) during unloading operation is taken as a ramp position where the head contacts a ramp. The ramp position thus determined is stored, and in unloading operation at the user-end, the head is retracted to the ramp position.
However, in the conventional technology, the control range of the servo information is narrow to facilitate the detection of a decrease in head speed. Consequently, the magnetic disk becomes vulnerable to disturbances (such as vibrations, jolts). Further, loss of friction of the ramp leads to a high probability of faulty ramp-position detection.